The following image shows the (incorrectly calibrated) antenna noise temperature measured by a fixed
3.05 m dish antenna as the Earth rotated for three days. Note that the same object is seen each day
at about the same time, with the peak slightly moving as the Earth revolves around the Sun.  
The object in the plots is Cygnus A. We are seeing the result of stars and dust falling 
into a black hole about 
600 million light years distant. Since this data was taken an error was found in the noise temperature formula. 
Antenna temperature is about 60 K. 



<p align="center"><img src="xgr1.jpg" alt="early radio astronomy"></p>
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